1. Field of the Invention
The present invention relates to a rotary electric apparatus, such as DC brushless motor and three-phase AC motor generator, which is generally called “synchronous machine,” and, in particular to the rotary electric apparatus which has an improved ability to reduce the ripples of torque that are generated and also reduce the noise (called “magnetic noise”) caused by pulsated drive current.
2. Description of the Related Art
A various types of rotary electric apparatuses have now been used, one type of which is proposed by (i) Japanese Patent publication No. 2672178, (ii) Japanese Patent publication No. 3028669, (iii) Japanese Patent Laid-open publication No. 9-182387, and (iv) Japanese Patent Laid-open publication No. 2003-284276.
Of these, the publications (i) to (iii) provide a skew structure arranged in a motor, in which even rotor members, each consisting of a magnetic rotor, are secured on a rotary shaft in a mutually adjacent manner such that the rotor members are shifted from each other along the rotary shaft by an angle corresponding to a half wavelength of a torque harmonic component of a predetermined order. Further, the forgoing publication (iv) also provides a motor provided with a rotor of skew arrangement type mentioned above, wherein a nonmagnetic member is inserted between mutually adjacent rotor members.
In the foregoing skewed rotary electric apparatus, a practical example can be provided such that the rotor members are skewed by an angle that corresponds to a half wavelength of a torque harmonic component of, for example, the sixth order (in the case of the three-phase type). This skew arrangement allows the torque harmonic component of this order to be opposite in phase between a first rotor part and a second rotor part. This skew arrangement aims at canceling the torque harmonic components from the two rotor parts.
However, it has been pointed out that such conventional skew arrangement structures are insufficient for canceling the torque harmonic components.